The present invention relates to an audio-decoder apparatus for decoding encoded audio signal, which is regenerated by a DVD player, a DVD-ROM driver or the like.
Conventionally, in a domain of audio decoder apparatus of this sort, there are a plurality of channel models (in other words, audio device sets), such as so-called “2-channel model”, “5.1-channel model” and the like. And a printed circuit substrate (PCB) comprised of a decoder for decoding the Dolby audio signal and a digital/analog (hereinafter referred to D/A) converter for audio signal has been used for each of the channel models.
FIGS. 4(a) and (b) show schematic diagrams of circuit substrates 1 and 2 for 2-channel and 5.1-channel (“channel” is referred to as “ch” in Figures) models of an audio decoder apparatus in the prior art. The circuit substrate 1 for 2-channel model comprises an MPEG (Moving picture Experts Group) decoder 3 and a D/A converter (DAC) 4 having a PLL (Phase-Locked Loop) built-in for a front sound signal. On the other hand, the circuit substrate 2 for 5.1-channel model comprises an MPEG decoder 3, a D/A converter (DAC) 4 PLL built-in for the front sound signal and D/A converters 5 and 6 without built-in PLL for a surrounding sound signal and a sub-woofer center sound signal. The MPEG decoder 3 and each of the D/A converters 4, 5 and 6 are connected through lines 7. FIG. 5(a) shows constitution of a speaker system in a 2-channel model system and FIG. 5 (b) shows constitution elements of speaker system in a 5.1-channel model system.
When such a conventional scheme of the circuit substrates is employed, the fabrication cost tends to be expensive because a plurality of circuit substrates has to be fabricated. Thus, in order to solve the problem of such expensive fabrication cost, it is known that employing standardized circuit substrates and the like for different audio systems enables a common hardware to be adapted in a variety of models. (Refer to Japanese Unexamined Patent Publication No. HEI 11-180221, for instance.)